The most popular method for the three-dimensional display by the prior art is one using a binocular parallax phenomenon. This method utilizes a principle that the human brain perceives a three-dimensional image when each eye sees one of two images that are measured at different angles. This method does not actually generate a three-dimensional image in space. Rather, parallax by the observer's eyes is utilized. Therefore, this method has disadvantages that various factors including arbitrary distribution of the viewer's position, binocular disparity due to deviations in the distance between the two eyes, vergence, fatigue accumulation in the eye, accommodation, the relative position change of the three-dimensional image due to viewer's movement, etc., are involved, and such factors must be considered in order to provide a proper three-dimensional display.
Holography is a three-dimensional display method that generates a real image in space. Holography has been used for three-dimensional image display very limitedly due to its technical complexity and high manufacturing cost.
U.S. Pat. No. 4,834,512 to Austin discloses a three-dimensional display having a two-dimensional display, a fluid-filled variable focusing lens, and control means for controlling the display and the lens. The two-dimensional display sequentially presents two-dimensional images representative of the cross sections of an object at different depths. The fluid-filled variable focusing lens is disposed in front of the two-dimensional display and has a membrane that responds to the pressure of the fluid within the lens. Austin's display has a disadvantage that the display is unsuitable for displaying realistic three-dimensional images since the focusing speed of the fluid-filled lens is slow.
U.S. Pat. No. 6,909,555 to Wohlstadter discloses an imaging method and system for creating a three-dimensional image from a two-dimensional image having a plurality of image points or pixels. The imaging system includes an array of variable focal length liquid micro-lenses formed on a self assembling monolayer, where each image point or pixel is in registered alignment with one or more micro-lenses in the array. The liquid micro-lenses formed on self assembling monolayer may have a strong hysteresis problem, which can cause failure of lenses to return to the original shape when the actuating force is disconnected. Also, these lenses require additional compound lens for correcting optical aberrations.
While utilizing a variable focal length lens for three-dimensional display is very promising, the conventional variable focal length lenses have limitation on their performance which includes focusing speed, range of focal length variation, optical focusing efficiency, aperture size, amount of aberration, production cost, etc.
A new three-dimensional image display method and device, which can meet demanding requirements including reducing eye fatigue, flexibility in viewing positions, providing three-dimensional images in the various perspectives without moving viewer's position, practicality of the relative distance between a three-dimensional image and the viewer, 2D/3D compatibility or exchangeability, color expression and resolution that equal or exceed those of HDTV, low manufacturing cost, and no significant data amount increase, have long been in need.